The explosion-protected housings typically form an ignition protection type “flameproof encapsulation” (Ex-d) within which electrical and/or electronic component parts or components are contained. Such electrical components can represent ignition sources for an explosive atmosphere present in the surrounding area outside of the housing. In such explosion-protected housings the pressure release device serves the purpose of establishing a pressure compensation between the housing interior and the surrounding area. It serves the purpose of limiting or reducing the pressure on the housing in the event of an explosion, which takes place within the housing, or also of compensating pressure differences to the surrounding area, for example by means of temperature changes. For this purpose, a gas-permeable connection is established between the interior of the housing and the surrounding area via the pressure release device. Simultaneously, the pressure release device ensures that flames, sparks or the like cannot reach from the interior of the housing to the outside into the explosive surrounding area. The housing as well as the pressure release device must thus be able to withstand an explosion pressure.
A pressure release device is known from U.S. Pat. No. 4,180,177 A, for example. In this document, a porous body is inserted in a pressure release passage. The porous body is gas-permeable. It is held in the pressure release passage so as to be clamped between ring flanges in flow-through direction.
A pressure release device which is designed with a similar principle is known from DE 2010 016 782 A1. A porous body is seized therein at a ring-shaped edge zone and is clamped tightly. By means of the clamping, a pore seal can also be attained in this edge zone. A hollow-cylindrical accommodating part, in which a pressure release passage is formed, serves to enclose the porous body. This hollow-cylindrical accommodating part can be inserted in the housing wall of an explosion-proof housing and can in particular be screwed in.